Mitsubishi 1992 3000GT, Service Manual

Page: 185 / 1308

MULTIPORT
On-Vehicle Inspection of MFI
FUEL INJECTION Components
OPERATION
Relay Operation
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Drives the fuel pump during cranking and engine operation.
When the ignition switch is set to START, current flows from the ignition switch through the
relay coil to ground. This turns on the MFI relay switch and drive power is supplied from the battery
through the MFI relay switch to the fuel pump.
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While the engine is running, the engine control module keeps the power transistor on and energizes
the MFI relay coil so that drive power is supplied to the fuel pump.
Fuel Pump Relay II Operation
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Change the fuel pump discharge in two stages by ON-OFF operation of the relay switch for fuel
pump relay II.
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If the amount of inlet air is small (the engine load is low), the engine control module turns on the
power transistor to energize the coil of fuel pump relay II, sending drive power to the fuel pump
through the resistor. If the amount of inlet air is large (the engine load is high), the engine control
module turns off the power transistor to send drive power directly to the fuel pump without passing
through the resistor.
INSPECTION
Using Scan Tool
<Fuel Pump>
Function
Item No. Operation Check condition Check item Normal condition
Actuator test 07 Fuel pump is
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Engine cranking Hold return hose with Pulsation is felt
driven to cir-
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Forced drive of fuel
fuel
fingers to feel pulsation
Check is made for
indicating fuel flow
above two conditions
Listen to pump operat- Operating sound
ing sound near fuel tank
is heard
<Fuel Pump Relay
Function Item No. Operation Check condition Normal condition
Actuator test 13 Turn the fuel pump relay Ignition switch: ON
II from OFF to ON
Operating sound is
heard.
HARNESS INSPECTION
check terminal
Check the fuel pump.
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Apply battery voltage to the
checking terminal and oper-
ate the pump.
Check the ground circuit of the
fuel pump.
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Fuel pump connector:
connected
Repair the
harness.
(B2
Ground)
TSB Revision